The relative importance of food aspiration in the development of pulmonary disease is poorly understood. This is, in part, because the amount of aspirated material in, and its removal from, the tracheopulmonary system cannot be adequately measured. Available tools for detecting airway aspiration, specifically barium fluoroscopy, are insufficient for detailing the fate of food aspirated through the glottis. Recent investigations employing radioisotope-tagged liquids have shown the usefulness of this technique for detecting and semi-quantifying aspiration in dysphagic individuals. However, these studies 1) ignored the depth of penetration and the rate of clearance from the lungs as measurable parameters and 2) lacked accurate quantification as tissue attenuation of radioactivity was not considered. Three concurrent lines of research will be pursued in this project. The first is the development of accurate methodologies using advanced scintigraphic techniques for measurement of radiotracer uptake in detecting and quantifying aspiration of liquid food. Quantification techniques will be subdivided into 1) measurement of volume of liquid aspirated; 2) measurement of depth of pulmonary penetration, and 3) measurement of rate of clearance of aspirated material from the lungs. The second line of research will be a controlled comparison of scintigraphic and standard videofluorographic techniques for detecting aspiration in a dysphagic stroke population. The third line of research will involve two related objectives. First, the aspiration quantification methods developed will be used in a dysphagic stroke population to determine the prevalence and severity of aspiration based on the amount aspirated, its depth of pulmonary penetration, and the rapidity of clearance of aspirated materials. Second, extensiveness of aspiration will be correlated with demographic and clinical characteristics in order to identify clinical predictors of aspiration severity. This research will establish an accurate means for measuring the extensiveness of pulmonary aspiration of foodstuffs. An understanding of the range of severity of aspiration in dysphagic individuals will set the stage for a future examination of factors influencing the risk of development of aspiration sequelae, particularly pneumonia. Consequently, this line of investigation has ultimate implications for the management of dysphagia and aspiration.